Hitherto, a hydrogen permeable membrane has been studied in its use in order to supply hydrogen to a section requiring hydrogen. As a hydrogen permeable membrane, one provided with adsorption, dissociation, diffusion, combining ability and the like is desired. A typical example of the hydrogen permeable membrane is one formed of palladium alloy. However, palladium is a noble metal and expensive, and therefore researches and developments are being extensively made on hydrogen permeable membranes formed of other metals such as vanadium alloy and niobium alloy.
Of these, it is recently studied that the hydrogen permeable membrane is used in a fuel cell system owing to elevation of interest in global environment. Specifically, in order to supply hydrogen gas to a fuel cell, the hydrogen permeable membrane has being studied as one to be used when hydrogen gas is separated from reformed gas after the reformed gas containing hydrogen is produced from liquid fuel.
The fuel cell generates electric power under electrochemical reaction using hydrogen as fuel and oxygen or air containing oxygen as oxidizing agent. In case of considering application to vehicles or the like, it is required to reduce the volume of a whole fuel cell system as small as possible.
Accordingly, it is desired that a fuel source is liquid as compared with gas, and the development of hydrogen permeable membranes to be useable for taking out hydrogen from liquid fuel is important.
As conventional hydrogen permeable membranes, one in which a coating film of a hydrogen separating metal is formed at the surface layer of a porous support member, for example. The hydrogen permeable membrane is improved in hydrogen permeating velocity as the thickness of the coating film decreases. Additionally, if the hydrogen permeable membrane can be thinner, the volume of the hydrogen separating apparatus is reduced. For example, if the thickness of the hydrogen permeable membrane is made 1/10, the hydrogen permeating performance is 10 times, so as to make it possible to make the volume of the hydrogen separating apparatus 1/10. In this case, the using amount of palladium becomes 1/100, making it possible to largely lower the cost regardless of using expensive palladium.
For these reasons, it is required to thin the hydrogen permeable membranes, making studies to thin hydrogen permeable membranes having no pin hole (see Patent Citation 1).
Studies have been made also on independent hydrogen permeable membranes. The independent hydrogen permeable membranes are not required to be formed as coating films on a porous support member, and therefore hydrogen permeable membranes having no pin hole can be formed upon being thinned as compared with the coating film-type hydrogen permeable membrane.
However, thinning the membrane makes it difficult to obtain a sufficient strength, so that a structure for supporting the membrane becomes necessary in order to compensate the strength of the hydrogen permeable membrane.
For example, the following hydrogen separation apparatus is proposed (see Patent Citation 2): The hydrogen separating apparatus includes an independent and metallic hydrogen permeable membrane through which hydrogen can be selectively permeable, and a support section disposed adjacent to the above-mentioned hydrogen permeable membrane. The above-mentioned support section includes a contact section having a contact surface at least a surface side opposite to the above-mentioned hydrogen permeable membrane, the contact surface being in contact with the above-mentioned hydrogen permeable membrane, and a non-contact section forming a gas passage without contacting. A wall surface of the above-mentioned contact section serving as an interface between the above-mentioned contact section and the above-mentioned non-contact section includes an obtuse angle surface at an end section of the above-mentioned contact surface, the obtuse angle surface being set to form an obtuse angle relative to the above-mentioned contact surface (see Patent Citation 2).    Patent Citation 1: Japanese Patent Provisional Publication No. 2002-52326    Patent Citation 2: Japanese Patent Provisional Publication No. 2003-165710